Rashi explains that Moshe Rabbeinu was telling the people that anointing Aharon and preparing him to serve as Kohen Gadol was not his own “idea.” He was following the instruction of the Almighty. Moshe was concerned that the people might suspect that he was acting either on his own behalf or on the behalf of his brother Aharon. He mitigated their concerns. While this may have “calmed” the people, Chazal relate that Moshe was still worried that he might personally benefit from the honor of investing Aharon into the Priesthood. This would constitute me’ilah, unlawfully benefiting from this holy endeavor….
